This invention relates to an articulated rotor for helicopters, in which the basic blade movements can be effected substantially exactly, and which at the same time is of considerable constructional simplicity.
Each blade of a rotor of this type is connected to its hub in such a manner as to allow it the freedom to swivel substantially about three fundamental axes. A first swivel movement takes place about a substantially horizontal axis to enable the blade to move in a vertical plane (variation of the flapping angle); a second swivel movement takes place about a vertical axis to enable the blade to move in a substantially horizontal plane (variation of the lead-lag angle); and finally a third swivel movement takes place about an axis coinciding with the longitudinal axis of the blade (variation of the pitch angle).
Various types of articulated rotor for helicopters are known in which each blade is connected to the hub by means of a kinematic linkage arranged to transmit to the hub the centrifugal force applied to each blade, but which allows each blade sufficient degrees of freedom to enable it to swivel about the three said axes. Such a kinematic linkage normally uses a number of rigid and/or deformable members connected variously together in such a manner as to give rise to rigid and resilient connections between the blade and hub. In particular, elastomer bearings are widely used as the deformable members in such a kinematic linkage.
However, rotors of the described type have the drawback of being considerably complicated because of the structure of said kinematic linkage, and if elastomer elements are used instead of rigid members for simplicity reasons, then such rotors have the drawback of not effecting the aforesaid three swivel movements in an exact manner from the kinematic viewpoint. Thus summarising, in constructions in which said kinematic linkage uses only rigid members (levers, frames, hinges, bearings and the like), rotors are obtained which are very complicated, heavy and costly; however if this structure is simplified by using deformable elements of elastomer material, the kinematic purity of the articulation between the blade and hub is impaired, such that certain movements do not become properly defined or undesirable constraints become introduced.